A preliminary study of extraction of sulphur and calcium from eggshell waste

Background: Egg shells take a year to decompose but are known to keep pests at bay. They contain many basic amino acids like cystine in reasonable quantities. Cystine being a dimer of cysteine contains a disulphide bond. This could be used as a source of sulphur. Objective: Our aim was to extract sulphur and carry out various tests to check the presence of both sulphur and calcium in egg shells. Using this knowledge the efficacy of calcium and sulphur as fungicides could be postulated. Methods: Egg shells were treated with 40% sodium hydroxide and lead acetate giving lead sulphide which confirmed the presence of sulphur in eggshell. Eggshells were then treated with 40% sodium hydroxide once again followed by treatment with 16 N nitric acid which led to the formation of sulphur powder. Further by testing we confirmed the presence of sulphur in the final powder. We also performed various reactions to check if calcium carbonate could be converted to calcium chloride and calcium hydroxide. Results: Maximum % concentration of sulphur (4.45%) was obtained when the volume of sodium hydroxide to nitric acid used was in the ratio of 3:2 and least % concentration (0.13%) was obtained when the ratio was 2:1. Conclusion: The method developed could be worked on to get more % concentration of sulphur and cannot be used alongside the industrial method of obtaining sulphur. However, obtaining calcium from egg shells shows a promising future.